The present invention relates to a new and improved method of controlling the start-up, the normal operation and the stopping of all spinning positions of an open-end spinning machine, and this invention also pertains to novel apparatus for implementing the aforesaid method.
During the normal operation of an open-end spinning machine the driven elements of each spinning position are driven by shafts and belts which extend over the entire machine length. With this arrangement the driven elements are in a speed ratio relative to one another which is constant and can be chosen as required by the spinning process. Thus, it is only necessary that a number of electric motors be kept operating at a certain constant speed, and there is not required any electrical function control. Operation of the motors is controlled by conventional switching relays. Such operation requires very low switching frequencies and results in high performance reliability.
In the case of a relay-controlled open-end spinning machine without automatic control of the start-up process, the yarn must be again manually re-spun or pieced-up after an interruption of the operation at each spinning position, since the spinning operation is only possible at speeds exceeding a minimum rotational speed of the rotor. Hence, for reasons of economy this starting spinning or piecing-up operation undertaken at modern machines is carried out automatically and simultaneously at the numerous spinning positions of the machine within a very short period of time. However, if the automatic piecing operation is to be made possible, then, there is required stopping of the machine in a strictly determined functional sequence, since re-piecing is only possible under certain conditions governed by the spinning process. The automatic start-up operation therefore also requires an automatic stopping of the machine.
Automatic starting and stopping of the machine is carried out by controlling different motors, clutches and brakes according to so-called start-stop programs. On high-speed modern day machines, such complicated control functions only can be performed by an electronic control unit. These electronic control units additionally can perform numerous auxiliary functions such as, for instance, counting the quantity of produced yarn, monitoring the vacuum in the rotor and monitoring the electrical voltage. But, of course, such an electronic control unit also controls the most frequently prevailing normal operation.
While without doubt the introduction of electronics for machine control applications has yielded many advantages, nonetheless a certain disadvantage exists. Although the theoretical life span of electronic components is several years, nonetheless they are considerably more susceptible to disturbances under the environmental conditions which prevail in practical use than, for instance, relay switches of very low switching frequencies. Thus, factors such as vibrations, humidity, electrical disturbances, material defects, undue handling and other reasons can cause unexpected premature failure of such components. Should such a disturbance occur, then usually the control unit automatically stops functioning and at the same time the machine is automatically stopped. Even if such disturbances rarely occur, nonetheless the entire machine stands idle throughout the repair time. Due to the lack of knowledge about and the usual dislike of the operating personnel against electronics, it is oftentimes the case that the damage cannot be repaired by using the mill's own resources, resulting in economically unbearable machine downtime periods.